Guide wires are used to guide a catheter for treating a body region at which a surgical operation such as PTCA (Percutaneous Transluminal Coronary Angioplasty) cannot be performed. Guide wires are also used to guide a catheter for treating a human body on a minimally invasive basis, or diagnosing a cardiovascular according to angiography. A guide wire used in PTCA is combined with a balloon catheter such that the distal end of the guide wire projects from the distal end of the balloon catheter, and is inserted together with the balloon catheter into a position near a constricted area of a blood vessel. Then, the guide wire guides the distal end of the balloon catheter to the stenosis area of the blood vessel.
Blood vessels oftentimes possess an intricately curved shape. Guide wires used to insert balloon catheters into such blood vessels are required to have flexibility and elasticity upon bending, pushability and torque transmission performance for transmitting a control action on the proximal end toward the distal end (these features will be collectively referred to as “steerability”), and kink resistance (fold resistance). Guide wire structures for achieving flexibility among the above features include a structure in which a metal coil having flexibility upon bending is wound around a core at the slender distal end of a guide wire and a structure in which a superelastic wire of Ni—Ti or the like is used as a guide wire core for giving flexibility and elasticity.
Conventional guide wires have a core made essentially of one material. For increased steerability of guide wires, the core is made of a material having a relatively high modulus of elasticity, which tends to make the distal end of the guide wire less flexible. If the core is made of a material having a relatively low modulus of elasticity for making the distal end of the guide wire more flexible, then the proximal end of the guide wire loses its steerability. It has been difficult to achieve both flexibility and steerability with one core material.